<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>

	</head>
	<body>
		<div class="box1" >
			
		</div>
		
		<script type="text/javascript">
			
			//获取div元素
			let divEle = document.getElementsByClassName('box1')[0];
			divEle.style.width = '300px';
			divEle.style.height = '300px';
			divEle.style.border = '1px solid red';
			divEle.style.borderRadius = '50%';
			
			divEle.innerHTML = ' <div style="border:1px solid green">我是小的div </div> '
		</script>
	</body>
</html>
